NOW I'm friggin perplexed... There is something, based on Python, that is periodically firing up and using Port 53.
I disabled Sabnzbd+, CouchPotato and SickBeard and kept checking 53, and it would pop up and clear, each time with different PID:
iMac:PlexConnect richard$ sudo lsof -i :53
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
Python 1175 root 4u IPv4 0xd9b7470eeb3a54eb 0t0 UDP 192.168.178.104:domain
iMac:PlexConnect richard$ sudo lsof -i :53
iMac:PlexConnect richard$ sudo lsof -i :53
Password:
iMac:PlexConnect richard$ sudo lsof -i :53
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
Python 2790 root 4u IPv4 0xd9b7470ef0ce305b 0t0 UDP 192.168.178.104:domain
iMac:PlexConnect richard$ sudo lsof -i :53
iMac:PlexConnect richard$ sudo lsof -i :53
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
Python 2846 root 4u IPv4 0xd9b7470eeb9e77fb 0t0 UDP 192.168.178.104:domain
iMac:PlexConnect richard$ sudo lsof -i :53
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
Python 2846 root 4u IPv4 0xd9b7470eeb9e77fb 0t0 UDP 192.168.178.104:domain
iMac:PlexConnect richard$ sudo lsof -i :53
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
Python 2846 root 4u IPv4 0xd9b7470eeb9e77fb 0t0 UDP 192.168.178.104:domain
iMac:PlexConnect richard$ sudo lsof -i :53
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
Python 2846 root 4u IPv4 0xd9b7470eeb9e77fb 0t0 UDP 192.168.178.104:domain
iMac:PlexConnect richard$ sudo lsof -i :53
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
Google 1348 richard 51u IPv4 0xd9b7470eeb9f3c8b 0t0 UDP 192.168.178.104:10629->176.67.84.19:domain
iMac:PlexConnect richard$ sudo lsof -i :53
iMac:PlexConnect richard$ sudo lsof -i :53
iMac:PlexConnect richard$ sudo lsof -i :53
iMac:PlexConnect richard$ sudo lsof -i :53
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
Python 2942 root 4u IPv4 0xd9b7470ef0ce305b 0t0 UDP 192.168.178.104:domain
iMac:PlexConnect richard$ sudo lsof -i :53
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
Python 2942 root 4u IPv4 0xd9b7470ef0ce305b 0t0 UDP 192.168.178.104:domain
iMac:PlexConnect richard$ sudo lsof -i :53
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
Python 2942 root 4u IPv4 0xd9b7470ef0ce305b 0t0 UDP 192.168.178.104:domain
iMac:PlexConnect richard$ sudo lsof -i :53
iMac:PlexConnect richard$ sudo lsof -i :53
iMac:PlexConnect richard$ sudo lsof -i :53
iMac:PlexConnect richard$ sudo lsof -i :53
iMac:PlexConnect richard$ sudo lsof -i :53
iMac:PlexConnect richard$ sudo lsof -i :53
iMac:PlexConnect richard$ sudo lsof -i :53
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
Python 2991 root 4u IPv4 0xd9b7470eeb9e09e3 0t0 UDP 192.168.178.104:domain
iMac:PlexConnect richard$ sudo lsof -i :53
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
Python 2991 root 4u IPv4 0xd9b7470eeb9e09e3 0t0 UDP 192.168.178.104:domain
iMac:PlexConnect richard$ sudo lsof -i :53
iMac:PlexConnect richard$ sudo lsof -i :53
iMac:PlexConnect richard$ sudo lsof -i :53
iMac:PlexConnect richard$ sudo lsof -i :53
iMac:PlexConnect richard$ sudo lsof -i :53
iMac:PlexConnect richard$ sudo lsof -i :53
iMac:PlexConnect richard$ sudo lsof -i :53
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
Python 3037 root 4u IPv4 0xd9b7470eeb9f3c8b 0t0 UDP 192.168.178.104:domain
iMac:PlexConnect richard$ sudo lsof -i :53
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
Python 3037 root 4u IPv4 0xd9b7470eeb9f3c8b 0t0 UDP 192.168.178.104:domain
iMac:PlexConnect richard$ sudo lsof -i :53
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
Python 3037 root 4u IPv4 0xd9b7470eeb9f3c8b 0t0 UDP 192.168.178.104:domain
iMac:PlexConnect richard$ sudo lsof -i :53
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
Python 3037 root 4u IPv4 0xd9b7470eeb9f3c8b 0t0 UDP 192.168.178.104:domain
iMac:PlexConnect richard$ sudo lsof -i :53
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
Python 3037 root 4u IPv4 0xd9b7470eeb9f3c8b 0t0 UDP 192.168.178.104:domain
iMac:PlexConnect richard$ sudo lsof -i :53
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
Python 3037 root 4u IPv4 0xd9b7470eeb9f3c8b 0t0 UDP 192.168.178.104:domain
iMac:PlexConnect richard$ sudo lsof -i :53
iMac:PlexConnect richard$ sudo lsof -i :53
iMac:PlexConnect richard$ sudo lsof -i :53
iMac:PlexConnect richard$ sudo lsof -i :53
iMac:PlexConnect richard$ sudo lsof -i :53
iMac:PlexConnect richard$ sudo lsof -i :53
iMac:PlexConnect richard$ sudo lsof -i :53
iMac:PlexConnect richard$ sudo lsof -i :53
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
Python 3100 root 4u IPv4 0xd9b7470eea6753c3 0t0 UDP 192.168.178.104:domain
iMac:PlexConnect richard$ sudo lsof -i :53
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
Python 3100 root 4u IPv4 0xd9b7470eea6753c3 0t0 UDP 192.168.178.104:domain
iMac:PlexConnect richard$ sudo lsof -i :53
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
Python 3100 root 4u IPv4 0xd9b7470eea6753c3 0t0 UDP 192.168.178.104:domain
iMac:PlexConnect richard$ sudo lsof -i :53
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
Python 3100 root 4u IPv4 0xd9b7470eea6753c3 0t0 UDP 192.168.178.104:domain
iMac:PlexConnect richard$ sudo lsof -i :53
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
Python 3100 root 4u IPv4 0xd9b7470eea6753c3 0t0 UDP 192.168.178.104:domain
iMac:PlexConnect richard$ sudo lsof -i :53
iMac:PlexConnect richard$ sudo lsof -i :53
iMac:PlexConnect richard$ sudo lsof -i :53
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
Python 3144 root 4u IPv4 0xd9b7470eea675b63 0t0 UDP 192.168.178.104:domain
iMac:PlexConnect richard$ sudo lsof -i :53
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
Python 3144 root 4u IPv4 0xd9b7470eea675b63 0t0 UDP 192.168.178.104:domain
iMac:PlexConnect richard$ sudo lsof -i :53
iMac:PlexConnect richard$ sudo lsof -i :53
iMac:PlexConnect richard$ sudo lsof -i :53
iMac:PlexConnect richard$ sudo lsof -i :53
iMac:PlexConnect richard$ sudo lsof -i :53
iMac:PlexConnect richard$ sudo lsof -i :53
iMac:PlexConnect richard$ sudo lsof -i :53
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
Python 3192 root 4u IPv4 0xd9b7470eea6753c3 0t0 UDP 192.168.178.104:domain
iMac:PlexConnect richard$ sudo lsof -i :53
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
Python 3192 root 4u IPv4 0xd9b7470eea6753c3 0t0 UDP 192.168.178.104:domain
iMac:PlexConnect richard$ sudo lsof -i :53
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
Python 3192 root 4u IPv4 0xd9b7470eea6753c3 0t0 UDP 192.168.178.104:domain
iMac:PlexConnect richard$ sudo lsof -i :53
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
Python 3192 root 4u IPv4 0xd9b7470eea6753c3 0t0 UDP 192.168.178.104:domain
iMac:PlexConnect richard$ sudo lsof -i :53
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
Python 3192 root 4u IPv4 0xd9b7470eea6753c3 0t0 UDP 192.168.178.104:domain
iMac:PlexConnect richard$ sudo lsof -i :53
iMac:PlexConnect richard$ sudo lsof -i :53
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
Python 3232 root 4u IPv4 0xd9b7470ef0ce305b 0t0 UDP 192.168.178.104:domain
iMac:PlexConnect richard$ sudo lsof -i :53
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
Python 3232 root 4u IPv4 0xd9b7470ef0ce305b 0t0 UDP 192.168.178.104:domain
iMac:PlexConnect richard$ sudo lsof -i :53
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
Python 3232 root 4u IPv4 0xd9b7470ef0ce305b 0t0 UDP 192.168.178.104:domain
iMac:PlexConnect richard$ sudo lsof -i :53
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
Python 3232 root 4u IPv4 0xd9b7470ef0ce305b 0t0 UDP 192.168.178.104:domain
iMac:PlexConnect richard$ sudo lsof -i :53
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
Python 3232 root 4u IPv4 0xd9b7470ef0ce305b 0t0 UDP 192.168.178.104:domain
iMac:PlexConnect richard$ sudo lsof -i :53
iMac:PlexConnect richard$ sudo lsof -i :53
iMac:PlexConnect richard$
And none of those PID's match those from my Activity Monitor / Network tab